Diaphragm means for subcalibre non-spinning projectiles



Sept. 1, 1959 H. o. DONNER 2,901,973

DIAPHRAGM MEANS FOR SUBCALIBRE NON-SPINNING PROJECTILES Filed Nov. 22, 1954 d///4 /AA/X// J IN VEN TOR. 624/: 0770 flan 415a ited States Paent DIAPGM MEANS FOR SUBCALIBRE NON-SPINNING PROJECTILES Hans Otto Donner, Tampere, Finland Application November 22, 1954, Serial No. 470,432

Claims priority, application Finland December 10, 1953 4 Claims. (Cl. 102-93) The present invention relates to diaphragm means for sub-calibre fin-stabilized projectiles, particularly such as are adapted to be fired from smooth-bored field mortars. The invention is particularly concerned with the stabilizing of projectiles to be fired from barrels of an internal diameter greater than the external diameter of the projectile. For improving firing range and accuracy when using sub-calibre projectiles of the kind stated, many proposals have been made, which are directed chiefly to means for centering the projectile relative the barrel bore. These improvements, however, have been attained at the cost of impaired outer configuration of the projectile and increased manufacturing dificulties.

The present invention eliminates the above mentioned defects while at the same time attaining a notable improvement over the prior art with consequent economy of production and improved firing range and accuracy.

This desired result is attained, in accordance with the present invention by utilizing as auxiliary means, in the barrel bore, when firing sub-calibre projectiles, a diaphragm means comprising essentially a funnel-shaped member for the rear end of the projectile and adapted to be inserted in the barrel bore and provided with an open tip end rearwardly directed when in said bore, an internal funnel surface conforming, at least at the mouth end thereof, to the external surface of the corresponding part of the rear end of the projectile for insuring centering of the projectile in the funnel-shaped member while maintaining the friction between the surfaces within desired limits, openings in the Walls of the member located rearwardly of the open end tip for permitting powder gases to issue therethrough, a ring shaped powder gas check packing abutting the bore wall at the funnel mouth end thereof, and centering means concentric with said internal funnel surface and adapted to extend from the outer wall of the funnel-shaped member to the bore wall for centering the internal funnel surface and projectile relative the barrel axis.

The means for centering the fore end of the funnelshaped member are advantageously provided at the funnel mouth portion thereof and preferably shaped so the outer surface about the funnel mouth of the said member will function both as centering means and as packing means.

For centering the rear end of the funnel shaped member the same is provided with, for example, at least three projecting pieces which are spaced apart to form equal angles therebetween and which extend to the bore wall, concentric with the internal funnel surface. In between the funnel surface and the rear end of the projectile there is provided some suitable matter adapted to promote sliding of the projectile.

A structure embodying the present invention is illustrated by way of example in the accompanying drawing which is an elevational view of a projectile in position within a mortar barrel and provided with a diaphragm means in accordance with the present invention and shown partly in longitudinal section.

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On the drawing, a smooth-bored mortar barrel A is shown in part. The diaphragm means includes a funnelshaped member B having an internal frusto-conical recess D for the rear end of a projectile E and an open tip end P. In the embodiment shown the open tip end of the funnel-shaped member has threaded thereto a tubular extension piece H with a bore hole advantageously somewhat greater in diameter than that of the tip end opening F and with holes K made in the walls thereof for passage of gases of combustion. To the other end of the tubular piece H is rigidly secured, by means of a threaded nut I, a centrally bored centering member G with radial fins G at least three in number. The front end of the funnelshaped member B or, at least, the fore end of the internal funnel surface of the member is centered by an outer peripheral surface G positioned about the funnel mouth and provided with a peripheral groove mounting a powder gas check packing C.

The diaphragm means according to the present invention is advantageously made of some suitable light metal.

What I claim is:

1. Diaphragm means for use with sub-calibre nonspinning projectiles adapted to be fired from a field mortar having a barrel with smooth internal bore, comprising a funnel-shaped member independent of and for accommodating the rear end of the projectile and adapted for being inserted into the barrel, said member defining a rear tip opening, said funnel-shaped member having a peripheral configuration at its front end conforming closely with the bore of the barrel and having at its front end a frusto-conical recess conforming at least at the mouth end thereof to the external shape of the rear end of the projectile to insure centering of the projectile in said funnel-shaped member and for releasably supporting the projectile, said funnel-shaped member defining openings located rearwardly of said rear tip opening for the passage of gases of combustion therethrough, spaced centering members extending from the funnel-shaped member to the wall of the barrel bore for centering said recess and the projectile relativethe barrel bore axis, and a powder gas check packing on the front end of the funnel-shaped member forming a gas tight seal with the barrel.

2. Means as in claim 1, wherein the rear end of the funnel-shaped member is provided with at least three centering projections concentric with the internal frustoconical recess and spaced apart to form equal angles therebetween and adapted to extend to the wall of the barrel bore forming the centering member.

3. Means according to claim 1, including a tubular extension piece secured to the rear end of the funnel-shaped member and having a bore hole wider than the rear tip opening of the funnel-shaped member and holes extendiing radially from the bore hole.

4. Means according to claim 1, including a tubular extension piece secured to the rear end of the funnelshaped member and having a bore hole wider than the rear tip opening of the funnel-shaped member and holes extending radially from the bore hole, one of the centering members being secured to the rear end of said extension and having fins extending radially therefrom to the wall of the barrel bore.

References Cited in the file of this patent UNITED STATES PATENTS 2,247,563 Spalding July 1, 1941 2,383,053 Fanger et al. Aug. 21, 1945 FOREIGN PATENTS 131,034 Great Britain Aug. 21, 1919 812,680 France Feb. 8, 1937 

